Mesh grounding on Korean substations means burying a grid of earth conductors under the site and measuring its earth resistance so the substation can operate safely. During an earth fault, large currents flowing into the ground create dangerous step and touch voltages; a dense grid keeps those voltages down to protect people and equipment. The grid has to go in right after excavation and before the hardcore layer, and it is very hard to fix once buried, so planning matters. This guide covers three stages: planning, installation and earth resistance measurement.
Contents
- Common Pre-Work Review
- 1. Planning
- 2. Installation
- NCS Mesh Grounding Points
- 3. Earth Resistance Measurement
- FAQ
- Reference Standards
- Summary
Common Pre-Work Review
Review the design (including architectural, mechanical and structural drawings), schedule, KEC, standard electrical specifications and design criteria, KESCO inspection criteria, the substation standard work procedure and KOSHA guides on earth conductors and earthing design. Prepare an earth resistance tester, soil resistivity tester, cable cutter and hydraulic compression tool, and hire an excavator. Materials are bare stranded copper, earth sleeves, lugs and exothermic welding kit (molds, handle clamps, powder, igniter). Store earthing materials so they are not crushed, deformed or corroded.
1. Planning
- Establish soil resistivity as the basis for earthing design and construction.
- Review the earthing calculation and drawings.
- Prepare the mesh grounding plan from that review.
- Check whether auxiliary electrodes are needed and whether their spacing from the grid can be achieved for the grid size.
- Confirm links to building and equipment earthing.
2. Installation
- Prepare to build to the mesh grounding drawings.
- Install the grid after building excavation and before laying hardcore.
- Connect grid conductors, rods and equipment earths according to the design and standard procedure to minimize electrical and mechanical stress.
- Check the local frost depth and bury the grid below it.
- Where there are piles, weld rebar to steel pipe piles, and connect concrete pile strands to the grid with compression sleeves.
- Fit waterproof sleeves where earth conductors from the main grid enter buildings.
NCS Mesh Grounding Points
| Item | Criterion |
|---|---|
| Timing | After building excavation, before hardcore |
| Burial depth | Below the local frost depth |
| Steel pipe piles | Weld rebar to the pile for earthing |
| Concrete piles | Connect pile strands to the grid with compression sleeves |
| Conductors entering buildings | Waterproof sleeves to stop moisture |
| Grid joints | Leave 200–300 mm of each conductor at the compression clamp, compress, then bend 90° |
| Auxiliary electrodes | Keep spacing appropriate to the grid size |
These values come from the considerations in the NCS competency unit. Target earth resistance and grid spacing follow the earthing calculation and client design standards.
3. Earth Resistance Measurement
- Measure earth resistance after installation and keep the records.
- Analyze the results and check for problems.
- If needed, plan reinforcement or improvements to the earthing method.
FAQ
When is the mesh grid installed?
After building excavation and before the hardcore layer. Access is difficult afterwards, so coordinate with civil works early.
Why bury the grid below frost depth?
Frozen soil has much higher resistivity, which weakens earthing performance. Check local frost depth and bury below it.
What if earth resistance is above target?
Analyze the cause and plan reinforcement such as additional auxiliary electrodes or an improved earthing method.
Reference Standards
- Electricity Business Act (전기사업법) — law.go.kr
- Electrical Safety Management Act (전기안전관리법) — law.go.kr
- Electric Technology Management Act (전력기술관리법) — law.go.kr
- Electrical Construction Business Act (전기공사업법) — law.go.kr
- Occupational Safety and Health Act (산업안전보건법) — law.go.kr
- Korea Electro-technical Code (KEC, 한국전기설비규정) — law.go.kr
- Technical Standards for Electrical Equipment (전기설비기술기준) — law.go.kr
- KEPCO design standards and substation construction practice; Korean Industrial Standards (KS)
- NCS competency unit Substation Mesh Grounding (Mesh 접지공사, 1901070324_22v2; NCS is Korea’s National Competency Standards) — ncs.go.kr
Summary
The most common mistakes are laying the grid after the hardcore because civil works pushed ahead, and forgetting pile bonding and waterproofing at building entries. Planning depends on soil resistivity and the earthing calculation; installation on timing, frost depth and joints; and measurement on records and reinforcement plans. Related guides: Substation Structural Grounding, Substation Equipment Grounding, Substation Structure Installation. A Korean version of this guide is available here.
This article restructures the Korean NCS competency unit ‘Substation Mesh Grounding’ (Mesh 접지공사, code 1901070324_22v2) as a practical reference. Actual work must follow applicable standards and the judgment of qualified professionals; always confirm specific values, deadlines and criteria against the latest regulations and client standards.
Written/reviewed by VOLT · Last updated 2026-10-26